A projection-type video-image-displaying device which collects white light from a light source and forms a light-emitting surface, disposes a rotary color filter in the vicinity of the light-emitting surface, collects emitted light from the color filter and makes the light incident on one light modulation element, and projects an image formed by the light modulation element onto a screen by a projection lens, is already known by Patent Literature 1 described later. That is, since the same color image with high resolution as that of a three-plate type is obtained by one liquid crystal panel, it is unnecessary to provide fine color filters on pixels on each panel. Thereby, a yield of the liquid crystal panel can be improved and costs of the device can be reduced. Further, a control device which controls the rotation of the rotary color filter to be synchronized with an image display by the liquid crystal panel switches to an off state a state of the image display of the liquid crystal panel set by being divided into a plurality of lots in a rotation direction of the filter in synchronization with a passage of a boundary between respective color filters of the filter. Thereby, the control device prevents a color mixture from generating a state in which a collected-light spot (light-emitting surface) lies across adjacent color filters.